Low sodium peritoneal dialysis solution

ABSTRACT

An improved peritoneal dialysis solution and methods of administering same to a patient are provided. Pursuant to the present invention, the sodium concentration in the solution is decreased thus causing sodium to be transported from the circulation to the peritoneal cavity. This provides for an improved ultrafiltration profile for the same initial osmolality when compared to standard solutions. Also, the same ultrafiltration profile as standard solutions can be achieved with lower initial osmolalities.

This is a division of application Ser. No. 08/205,304, filed on Mar. 3,1994, U.S. Pat. No. 5,589,197, which is a continuation-in-part of U.S.Ser. No. 08/130,968, filed Oct. 4, 1993, abandoned.

BACKGROUND OF THE INVENTION

The present invention relates generally to peritoneal dialysis. Morespecifically, the present invention relates to peritoneal dialysissolutions.

It is known to use dialysis to support a patient whose renal functionhas decreased to the point where the kidneys no longer sufficientlyfunction. Two principal dialysis methods are utilized: hemodialysis; andperitoneal dialysis.

In hemodialysis, the patients blood is passed through an artificialkidney dialysis machine. A membrane in the machine acts as an artificialkidney for cleansing the blood. Because it is an extracorporealtreatment that requires special machinery, there are certain inherentdisadvantages with hemodialysis.

To overcome the disadvantages associated with hemodialysis, peritonealdialysis was developed. Peritoneal dialysis utilizes the patient's ownperitoneum as a semi-permeable membrane. The peritoneum is themembranous lining of the abdominal cavity that due to a large number ofblood vessels and capillaries is capable of acting as a naturalsemi-permeable membrane.

In peritoneal dialysis, a dialysis solution is introduced into theperitoneal cavity utilizing a catheter. After a sufficient period oftime, an exchange of solutes between the dialysate and the blood isachieved. Fluid removal is achieved by providing a suitable osmoticgradient from the blood to the dialysate to permit water outflow fromthe blood. This allows the proper acid-base electrolyte and fluidbalance to be returned to the blood and the dialysis solution is simplydrained from the body cavity through the catheter.

Although many advantages to peritoneal dialysis exist, one of thedifficulties that has been encountered is providing a suitable amount ofosmotic agent. What is required is achieving a sufficient osmoticgradient. The osmotic agent is used in a dialysis solution to maintainthe osmotic gradient that is required to cause the transport of waterand its accompanying toxic substances across the peritoneum into thedialysis solution.

Using dextrose as an osmotic agent is known. Dextrose is fairly safe andis readily metabolized if it enters the blood. However, one of theissues with respect to dextrose is that due to its small size, it israpidly transported from the peritoneal cavity. Because dextrose crossesthe peritoneum so rapidly, the osmotic gradient is dissipated within twoto three hours of infusion, leading to the loss of ultrafiltration.

A disadvantage of the rapid uptake of glucose by the blood is that itcan represent a large proportion of the patient's energy intake. Withrespect to, for example a diabetic patient, this can represent a severemetabolic burden to a patient whose glucose tolerance is alreadyimpaired. Dextrose can also cause problems with respect to hyperglycemiaand obesity.

Typical peritoneal dialysis solutions contain sodium in a concentrationof 132 mEq/L and dextrose at a concentration of 1.5 to 4.25% by weight.The solutions rely on a high initial solution osmolality to affect thetransport of water (metabolic waste products) from the circulation tothe peritoneal cavity. Such a solution results in a daily absorption of150 to 300 grams of glucose from the dialysate in the typical peritonealdialysis patient.

Further, with respect to the sodium levels, most hypertensive end stagerenal patients are volume and sodium overloaded. Current peritonealdialysis solutions do not adequately control blood pressure, becauseamong other things they do not remove enough sodium. Still further, anissue arises with respect to fluid intake because renal patients mustcontrol their fluid intake.

Therefore, a need exists for an improved peritoneal dialysis solution.

SUMMARY OF THE INVENTION

The present invention provides an improved peritoneal dialysis solution.Pursuant to the present invention, the sodium concentration in thesolution is decreased to below the patient's plasma concentrations ofsodium, thus causing sodium to be transported from the circulation tothe peritoneal cavity. This yields an increased ultrafiltration volumefor the same initial osmolality. Pursuant to the present invention, areduced amount of osmotic agent can be used to achieve equivalentultrafiltration.

To this end, a peritoneal dialysis solution comprising an osmotic agentand sodium in a concentration that is less than a sodium plasmaconcentration in the patient is provided. The osmotic agent is chosenfrom the group consisting of: amino acids; polypeptides; polyglucose;and glycerol.

In an embodiment, the peritoneal dialysis solution generally comprises 0to about 200 (mOsm/L) of an osmotic agent and includes:

0.0 to about 4.0 (% w/v) dextrose;

0 to about 120 (meq/L) sodium;

0 to about 100 (meq/L) chloride;

0 to about 45 (meq/L) lactate;

0 to about 45 (meq/L) bicarbonate;

0.0 to about 4.0 (meq/L) calcium; and

0.0 to about 4.0 (meq/L) magnesium.

In an embodiment, the peritoneal dialysis solution has a totalosmolality of 300 to about 500.

In an embodiment of the peritoneal dialysis solution, the sodiumcomprises approximately 35 to about 125 (meq/L).

In a further embodiment, the present invention provides a method formanufacturing a peritoneal dialysis solution comprising the steps ofreducing the concentration of sodium present in the solution below 132(meq/L) to cause an equivalent ultrafiltration volume with a reducedinitial solution osmolality (when compared to normal peritoneal dialysisfluid) or an increased ultrafiltration volume with the same initialsolution osmolality (when compared to normal peritoneal dialysis fluid).

In another embodiment, the present invention provides a method forproviding peritoneal dialysis to a patient comprising the steps ofadministering a solution including sodium and an osmotic agent chosenfrom the group consisting of polypeptides, polyglucose, amino acids andglycerol. The sodium level is less than a plasma sodium concentration ofthe patient to cause an equivalent ultrafiltration volume with a reducedinitial solution osmolality (when compared to normal peritoneal dialysisfluid) or an increased ultrafiltration volume with the same initialsolution osmolality (when compared to normal peritoneal dialysis fluid).

In yet another embodiment, the present invention provides a method forreducing hypertension in a dialysis patient at risk of same. The methodincludes the step of administering to a hypertensive dialysis patient aperitoneal dialysis solution including an osmotic agent and sodium in aconcentration that is less than a sodium concentration in thehypertensive dialysis patient who is to receive the solution.

The peritoneal dialysis solution can be designed to be used in a patientwho receives only one dwell a day of the low sodium solution or multipledwells a day.

An advantage of the present invention is to provide an improvedperitoneal dialysis solution.

Still further, an advantage of the present invention is to provide animproved method for providing dialysis to a patient.

A further advantage of the present invention is to provide a peritonealdialysis solution with lower sodium concentrations that providesultrafiltration over a longer period of time for the same startingosmolality.

Furthermore, an advantage of the present invention is to provide aperitoneal dialysis solution which provides a decreased glucose load tothe patient.

Another advantage of the present invention is to provide a peritonealdialysis solution with reduced sodium concentrations.

Still further, an advantage of the present invention is to provide aperitoneal dialysis solution with lower sodium concentrations used incombination with dextrose, that achieves comparable ultrafiltrationprofiles at lower initial osmolalities.

Moreover, an advantage of the present invention is to provide aperitoneal dialysis solution that helps to preserve the normal functionsof peritoneal cells such as macrophages, fibroblasts and mesothelialcells.

Additionally, an advantage of the present invention is to provide aperitoneal dialysis solution with an increased ultrafiltration volumeand an improved volume profile.

Another advantage of the present invention is to provide a peritonealdialysis solution that can be used for the overnight dwell in ContinuousAmbulatory Peritoneal Dialysis (CAPD).

Still further, an advantage of the present invention is to provide aperitoneal dialysis solution that will increase the amount of sodiumthat is removed from the patient.

Furthermore, an advantage of the present invention is to provide aperitoneal dialysis solution that will reduce patient's fluid intake.

Yet another advantage of the present invention is to provide anintraperitoneal solution that can improve the management of bloodpressure and fluid volume for congestive heart disease patients.

Another advantage of the present invention is to provide a peritonealdialysis solution that can be used advantageously for AutomatedPeritoneal Dialysis (APD).

Moreover, another advantage of the present invention is to provide aperitoneal dialysis solution that may be used to correct overhydrationof a patient.

Yet another advantage of the present invention is to provide aperitoneal dialysis solution that may be used to control hypertension.

Additional features and advantages of the present invention aredescribed in, and will be apparent from, the detailed description of thepresently preferred embodiments and from the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates, graphically, net ultrafiltration versus time for atypical peritoneal dialysis solution and one constructed pursuant to thepresent invention, both solutions having the same initial osmolality.

FIG. 2 illustrates, graphically, dialysate osmolality versus time for atypical peritoneal dialysis solution and one constructed pursuant to thepresent invention, both solutions having the same initial osmolality.

FIG. 3 illustrates, graphically, the body weight results for thepatients evaluated in accordance with Experiment No. 2.

FIG. 4 illustrates, graphically, total drainage volume (TDV) measured inml/day for the patients evaluated in accordance with Experiment No. 2.

FIG. 5 illustrates, graphically, blood pressure (BP) measured in mmHgfor the patients evaluated in accordance with Experiment No. 2.

FIG. 6 illustrates, graphically, trans-peritoneal sodium removalmeasured in mEq/day for patients evaluated in accordance with ExperimentNo. 2.

FIG. 7 illustrates, graphically, serum sodium levels measured in mEq/1for the patients evaluated in accordance with Experiment No. 2.

FIG. 8 illustrates, graphically, plasma osmolality measured in mOsm/kgH₂ O for the patients evaluated in accordance with Experiment No. 2.

FIG. 9 illustrates, graphically, plasma atrial natriuretic peptide (ANP)measured in pg/ml for the patients evaluated in accordance withExperiment No. 2.

FIG. 10 illustrates, graphically, levels of c-GMP measured in pg/ml forthe patients evaluated in accordance with Experiment No. 2.

FIG. 11 illustrates, graphically, plasma atrial activity (PRA) measuredin ng/ml/hr for the patients evaluated in accordance with Experiment No.2.

FIG. 12 illustrates, graphically, plasma aldosterone (PAt) measured inpg/ml for the patients evaluated in accordance with Experiment No. 2.

FIG. 13 illustrates, graphically, plasma norepinephrine (NEp) measuredin pg/ml for the patients evaluated in accordance with Experiment No. 2.

FIG. 14 illustrates, graphically, plasma vasopressin (AVP) measured inpg/ml for the patients evaluated in accordance with Experiment No. 2.

DETAILED DESCRIPTION OP THE PRESENTLY PREFERRED EMBODIMENTS

The present invention provides an improved peritoneal dialysis solutionthat contains a reduced sodium concentration, less than 132 meq/L. In apreferred embodiment, the sodium concentration is present in an amountequal to or less than 120 mEq/L. The concentration of sodium is lowerthan the normal plasma sodium concentration of the patient(140-145mmol/L), and thus sodium is transported from the circulation tothe peritoneal cavity. Unexpectedly, an increased ultrafiltration volumeand an improved volume profile with time may be achieved pursuant to thepresent invention with a low sodium peritoneal dialysis solution havingthe same initial osmolality as compared to a solution having a moreconventional sodium concentration.

As illustrated in FIG. 1 (which will be discussed in more detail infra),dialysis with the low sodium solution of the present invention, havingthe same initial osmolality as a solution with more conventional sodiumconcentrations unexpectedly results in an increased ultrafiltrationvolume and a sustained volume profile with time. Additionally, using thelow sodium solution of the present invention provides for an increasedremoval of sodium from the patient. The increased ultrafiltrationprofile is observed to occur even though the dialysate osmolalities ofboth solutions remains the same (see FIG. 2 discussed in more detailinfra).

Pursuant to the present invention, any osmotic agent can be used in thesolution. For example, dextrose, glycerol, polyglucose, polypeptides andamino acids can be used as the osmotic agent. It is envisioned, that theperitoneal dialysis solution of the present invention with reducedsodium concentrations can be used with unique advantages for thefollowing applications: for fluid overloaded patients; for sodiumoverloaded patients; for patients with ultrafiltration failure; forhypertensive patients; with high molecular weight osmotic agents todecrease glucose load and osmolality; for long dwells--greater than sixhours for example APD daytime dwell and CAPD overnight dwell; and forchronic congestive heart failure patients.

It has been found that if glucose is used as the osmotic agent that theglucose load to the CAPD (continuous ambulatory peritoneal dialysis) orAPD (automated peritoneal dialysis) patient can be reduced with a lowsodium concentration. This is because when a low sodium concentration isused in combination with dextrose, one can achieve ultrafiltrationprofiles comparable to a typically higher dextrose solution. Indeed,dextrose can be eliminated when the low sodium concentration solution isused in combination with other osmotic agents such as glycerol,polyglucose, polypeptides, and amino acids.

Additionally, the use of peritoneal dialysis solutions with low sodiumconcentrations causes the transport of sodium and its counter ion fromthe circulation to the peritoneal cavity. Thus, when used in combinationwith a larger, slower transporting osmotic agent (polypeptides,polyglucose, etc.) the ultrafiltration profile will be flatter. In thisregard, the osmotic gradient will be maintained for longer periods oftime. Thus, solutions of this kind are advantageous for longer dwellssuch as CAPD overnight or APD daytime dwells.

FIG. 1 illustrates actual net ultrafiltration in patients, over time, ofa typical peritoneal dialysis solution and a solution constructedpursuant to the present invention pursuant to the protocol set forth inthe experiment infra. FIG. 1 demonstrates the increased ultrafiltrationvolume and sustained volume achieved with the present invention.

It has been noted that higher initial osmolalities of current peritonealdialysis solutions can impair host defense mechanisms against infectionby suppressing the normal functions of peritoneal cells (macrophages,fibroblasts, mesothelial cells). An advantage of the present inventionis that when low sodium concentrations are used in combination withdextrose, comparable ultrafiltration profiles can be achieved at a lowerinitial osmolality; this thus assists in restoring the normal functionsof peritoneal cells.

Another advantage of the present invention is that a low sodiumconcentration will increase the amount of sodium that is removed fromthe patient. The low sodium solution of the present invention increasesthe amount of sodium that is removed from the patient. By removing moresodium, the renal patient's restrictions on salt intake can be relaxed.Thus, renal patients could include more salt in their diet which wouldtend to increase protein intake and thus, an improved nutritionalstatus.

The peritoneal dialysis solution of the present invention can generallyhave a profile such as follows:

    ______________________________________                                        Dextrose (% w/v)    0.0-4.0                                                   Sodium (mEq/L)       0-130                                                    Chloride (Meq/L)     0-100                                                    Lactate (mEq/L)      0-45                                                     Bicarbonate (mEq/L)  0-45                                                     Calcium (mEq/L)     0.0-4.0                                                   Magnesium (mEq/L)   0.0-4.0                                                   Total osmolality (mOsm/L)                                                                         300-500                                                   ______________________________________                                    

Solution containing an osmotic agent other than dextrose composition:

    ______________________________________                                        Osmotic agent (mOsm/L)                                                                             0-200                                                    Sodium (mEq/L)       0-130                                                    Chloride (mEq/L)     0-100                                                    Lactate (mEq/L)      0-45                                                     Bicarbonate (mEq/L)  0-45                                                     Calcium (mEq/L)     0.0-4.0                                                   Magnesium (mEq/L)   0.0-4.0                                                   Total osmolality (mOsm/L)                                                                         300-500                                                   ______________________________________                                    

More specifically, the peritoneal dialysis solutions have preferredranges as follows:

Composition Ranges for Low Sodium Solutions Used for All Dwells

Solution containing dextrose:

    ______________________________________                                        Dextrose (% w/v)    1.0-4.0                                                   Sodium (mEq/L)       90-130                                                   Chloride (mEq/L)    39-95                                                     Combination of Lactate and                                                                        30-45                                                     Bicarbonate (mEq/L)                                                           Calcium (mEq/L)     0.0-4.0                                                   Magnesium (mEq/L)   0.0-2.0                                                   Total Osmolality (mOsm/L)                                                                         300-500                                                   ______________________________________                                    

Solution containing an osmotic agent other than dextrose or containingdextrose in combination with another osmotic agent:

    ______________________________________                                        Osmotic Agent (mOsm/L)                                                                             1-200                                                    Dextrose (% w/v)    1.0-4.0                                                   Sodium (mEq/L)       90-130                                                   Chloride (mEq/L)    39-95                                                     Combination of Lactate and                                                                        30-45                                                     Bicarbonate (mEq/L)                                                           Calcium (mEq/L)     0.0-4.0                                                   Magnesium (mEq/L)   0.0-2.0                                                   Total Osmolality (mOsm/L)                                                                         300-500                                                   ______________________________________                                    

Composition Ranges for Low Sodium Solutions Used for Only One Dwell perDay

    ______________________________________                                        Dextrose (% w/v)    1.0-4.0                                                   Sodium (mEq/L)       35-120                                                   Chloride (mEq/L)     0-85                                                     Combination of Lactate and                                                                        30-45                                                     Bicarbonate (mEq/L)                                                           Calcium (mEq/L)     0.0-4.0                                                   Magnesium (mEq/L)   0.0-2.0                                                   Total Osmolality (mOsm/L)                                                                         300-500                                                   ______________________________________                                    

Solution containing an osmotic agent other than dextrose or containingdextrose in combination with another osmotic agent:

    ______________________________________                                        Osmotic agent (mOsm/L)                                                                             1-200                                                    Dextrose (% w/v)    1.0-4.0                                                   Sodium (mEq/L)      35-85                                                     Chloride (mEq/L)     0-100                                                    Combination of Lactate and                                                                        30-45                                                     Bicarbonate (mEq/L)                                                           Calcium (mEq/L)     0.0-4.0                                                   Magnesium (mEq/L)   0.0-4.0                                                   Total Osmolality (mOsm/L)                                                                         300-500                                                   ______________________________________                                    

Preferred Composition Ranges for Low Sodium Solutions Used for AllDwells

Sodium containing dextrose with the following composition:

    ______________________________________                                        Dextrose (% w/v)    1.0-4.0                                                   Sodium (mEq/L)      100-125                                                   Chloride (mEq/L)    55-87                                                     Combination of Lactate and                                                                        35-40                                                     Bicarbonate (mEq/L)                                                           Calcium (mEq/L)     2.5-3.5                                                   Magnesium (mEq/L)   0.5-1.5                                                   Total Osmolality (mOsm/L)                                                                         300-500                                                   ______________________________________                                    

Solution containing an osmotic agent other than dextrose or containingdextrose in combination with another osmotic agent:

    ______________________________________                                        Osmotic agent (mOsm/L)                                                                             1-200                                                    Dextrose (% w/v)    1.0-4.0                                                   Sodium (mEq/L)      100-125                                                   Chloride (mEq/L)    55-87                                                     Combination of Lactate and                                                                        35-40                                                     Bicarbonate (mEq/L)                                                           Calcium (mEq/L)     2.5-3.5                                                   Magnesium (mEq/L)   0.5-1.5                                                   Total Osmolality (mOsm/L)                                                                         300-500                                                   ______________________________________                                    

Preferred Composition Ranges for Low Sodium Solutions Used for One Dwellper Day

Solution containing dextrose:

    ______________________________________                                        Dextrose (% w/v)    1.0-4.0                                                   Sodium (mEq/L)       35-120                                                   Chloride (mEq/L)     3-82                                                     Combination of Lactate and                                                                        35-40                                                     Bicarbonate (mEq/L)                                                           Calcium (mEq/L)     2.5-3.5                                                   Magnesium (mEq/L)   0.5-1.5                                                   Total Osmolality (mOsm/L)                                                                         300-500                                                   ______________________________________                                    

Solution containing an osmotic agent other than dextrose or containingdextrose in combination with another osmotic agent:

    ______________________________________                                        Osmotic agent (mOsm/L)                                                                             1-200                                                    Dextrose (% w/v)    1.0-4.0                                                   Sodium (mEq/L)       35-120                                                   Chloride (mEq/L)     3-82                                                     Combination of Lactate and                                                                        35-40                                                     Bicarbonate (mEq/L)                                                           Calcium (mEq/L)     2.5-3.5                                                   Magnesium (mEq/L)   0.5-1.5                                                   Total Osmolality (mOsm/L)                                                                         300-500                                                   ______________________________________                                    

By way of example, and not limitation, specific examples of peritonealsolutions of the present invention are as follows:

Examples of Specific Compositions for Low Sodium PD Solutions

                                      TABLE NO. 1                                 __________________________________________________________________________          Dextrose                                                                            Sodium                                                                              Lactate                                                                             Chloride                                                                            Calcium                                                                             Magnesium                                                                            Total Osm                          Solution                                                                            (% w/v)                                                                             (mEq/L)                                                                             (mEq/L)                                                                             (mEq/L)                                                                             (mEq/L)                                                                             (mEq/L)                                                                              (mOsmol/L)                         __________________________________________________________________________    1     1.5   100   40    63    2.5   0.5    280                                2     1.5   110   40    73    2.5   0.5    300                                3     1.5   120   40    83    2.5   0.5    320                                4     1.5   125   40    88    2.5   0.5    330                                5     2.5   100   40    63    2.5   0.5    331                                6     2.5   105   40    69    3.5   0.5    342                                7     2.5   110   40    73    2.5   0.5    351                                8     2.5   120   40    83    2.5   0.5    371                                9     2.5   125   10    88    2.5   0.5    381                                10    2     100   40    63    2.5   0.5    306                                11    2     110   40    73    2.5   0.5    326                                12    2     120   40    83    2.5   0.5    346                                13    2     125   40    88    2.5   0.5    356                                14    3     100   40    63    2.5   0.5    356                                15    3     110   40    73    2.5   0.5    376                                16    3     125   40    83    2.5   0.5    396                                17    3     125   40    88    2.5   0.5    406                                18    2.2   115   40    78    2.5   0.5    346                                19    2.8   100   40    63    2.5   0.5    346                                20    3.6   100   35    70    3.5   1.5    389                                __________________________________________________________________________

By way of example, and not limitation, experiments using the presentinvention will now be given:

Experiment #1

The effects of low sodium concentration dialysates and normal sodiumconcentration dialysate, on the peritoneal fluid, sodium transport, theextracellular volumes and plasma volume in CAPD patients was evaluated.

STUDY PRODUCTS

Trial product (ULNaD)

Two liters of peritoneal dialysis solution with:

(1) sodium=100 mEq/1, calcium=3.5 mEq/1, magnesium=1.5 mEq/1,chloride=70 mEq/1, 1lactate=35 mmol/1, glucose=180 mmol/1, dextran 70=1g/l,

(2) osmolarity=384 mOsmol/1.

Control Solution (NNaD)

Two liters of commercially available peritoneal dialysis solution(Dianeal®2.5%) with:

(1) sodium=182 mEq/1, calcium=3.5 mEq/1, magnesium=1.5 mEq/1,chloride=102 mEq/1, lactate=35 mmol/1, glucose=126 mmol/1, dextran=70 1g/l,

(2) osmolarity=384 mOsmol/1.

STUDY DESIGN

Six stable CAPD patients were randomized in 2 groups of 3 patients. Twoperitoneal permeability tests with a duration of 6 hrs were performedwithin one week in all patients. One group of patients was investigatedusing the trial solution on the first examination, the other group withthe control solution during the first test. The other solution was usedduring the second test, allowing paired observations.

Before instillation of the trial/control solution, the peritoneal cavitywas rinsed with dialysate with the trial solution when the trialsolution was used and with the control solution when the controlsolution was used. Dialysate samples were taken before instillation and10, 20, 30, 60, 120, 180, 240, and 360 minutes after instillation of thetest solution. Blood samples were taken at: -1080, -1070, 0, 60, 120,180, 240 and 360 minutes. At -1080 minutes (18 hrs before the test)inulin (Inntest®) (60 mg/kg) was given intravenously to measureextracellular volume and plasma volume. At t=0 minutes, 20 ml dextran 1(Promitan®) (150 mg/ml) was given to prevent an anaphylactic reaction ondextran 70. At the end of the dwell period, the peritoneal cavity wasrinsed once (control or trial solution) to allow calculation of theresidual volume after drainage. All patients were provided with astandard meal of=1000 mg sodium and 500 calories before the test dwell.

STUDY PROCEDURES

A. Patient Selection

Criteria for selection

a. Aged at least 18 years

b. Patients established on CAPD for at least 8 months

Criteria for exclusion

a. Patients with peritonitis, or receiving antibiotics for peritonitis,within the previous 30 days.

b. Patients with an allergic reaction on dextran during previousexaminations.

c. Patients with congestire heart failure.

Laboratory

a. Parameters of plasma/blood

Inulin, sodium, potassium, chloride, calcium, magnesium, total protein,hemoglobin, hematocrit, glucose, urea, creatinine, urate, osmolarity,dextran antibodies, β₂ -microglobulin, albumin, transferring, IgG, IgA,and e2-macroglobulin.

b. Parameters of dialysate

Volume, inulin, sodium, potassium, chloride, calcium, magnesium,glucose, urea, creatinine, urate, osmolarity, β₂ -microglobulin,albumin, transferrin, IgG, IgA and α₂ -macroglobulin

c. Parameters of urine

Urinary production at -1080, from -1080 to 0 and from 0 to 240 minutes.Inulin, sodium, potassium, creatinine.

Results

The Figures illustrate the results of the study.

FIG. 1: Net ultrafiltration as a function of time. Results obtained from6 patients tested with both a regular PD solution (filled circles) and alow sodium PD solution having the same initial osmolality (emptycircles). Concentrations of glucose and sodium in these solutions areoutlined in the following table:

    ______________________________________                                        Solute           Regular  Low Sodium                                          ______________________________________                                        Glucose (mOsm/L) 126      180                                                 Sodium (mOsm/L)  132      100                                                 Total Osm (mOsm/L)                                                                             384      384                                                 ______________________________________                                    

FIG. 2: Dialysate osmolalities as a function of time. Results obtainedfrom 6 patients tested with both a regular PD solution (filled circles)and a low sodium PD solution having the same initial osmolality (emptycircles). Glucose and sodium concentrations are the same as shown in thetable above.

Experiment #2

The effects of using low sodium concentration dialysates instead ofnormal sodium concentration dialysate in hypertensive patients wasevaluated.

Table 2 below sets forth the nine patients evaluated in this experiment.All of the patients were hypertensive and four of them were takinganti-hypertensive drugs at the time of this experiment. Daily saltintakes were 7-10 grams. Prior to the experiment, the patients wereusing standard dialysate exchanging four bags daily.

                                      TABLE 2                                     __________________________________________________________________________                               standard        low Na         study               No  Sex Age CAPD (m)                                                                             UV (ml/day)                                                                           dialysate       dialysate      (w)                 __________________________________________________________________________    1   M   51  40 CGN 0       2.5% D × 4                                                                              2.5% D × 4                                                                             1                   2   M   60  28 DM  200     2.5% D × 4                                                                              2.5% D × 4                                                                             2                   3   F   40  4  CGN 1000    1.5% D × 4                                                                              1.5% D × 4                                                                             4                   4   M   43  29 CGN 350     1.5% D × 3 + 4.25% D × 1                                                          1.5% D × 1 + 2.5% D                                                     × 3      4                   5   F   48  15 CGN 200     1.5% D × 2 + 2.5% D × 2                                                           1.5% D × 1 + 2.5% D                                                     × 3      4                   6   M   34  12 CGN 350     2.5% D × 4                                                                              2.5% D × 4                                                                             4                   7   M   34  22 CGN 1000    1.5% D × 2 + 2.5% D × 2                                                           1.5% D × 2 + 2.5% D                                                     × 2      4                   8   M   46  65 CGN 0       1.5% D × 1 + 2.5% D × 3                                                           1.5% D × 1 + 2.5% D                                                     × 3      4                   9   M   32  7  CGN 800     1.5% D × 3 + 2.5% D × 1                                                           1.5% D × 3 + 2.5% D                                                     × 1      4                   __________________________________________________________________________

Method

Low sodium dialysate (120mEq/1) was used four times daily up to fourweeks, instead of standard dialysate. Body wt (kg), total drainagedvolume (TDV:ml/day) and blood pressure (BP:mmHg) were measured daily.Total daily trans-peritoneal sodium removals (Na removal:MEq/day) weremeasured before and the last day of the study. Blood samples were takenevery week for the measurement of serum sodium levels (mEq/1), plasmaosmolality (mOsm/kgH20) and vasoactive humoral factors, which wereplasma atrial natriuretic peptide (ANP:pg/ml), plasma renin activity(PRA:ng/ml/hr), plasma aldosterone (PAC:pg/ml), plasma norepinephrine(NEp:pg/ml), plasma vasopressin (AVP:pg/ml) and c-GMP(pg/ml). BP wasmeasured at the resting supine position in the early morning. Blood waswithdrawn at the time of out-patients clinic, after lying on the bedmore than 15 min.

Subjective symptoms and objective signs were examined at theout-patients clinic every week.

Results

Two patients were dropped out of the study, before the expiration offour weeks, because of overhydration due to inadequate ultrafiltration(patient No. 1), and progression of general fatigue due to hyponatremia(patient No. 2). The other seven cases used low sodium dialysate forfour weeks without any adverse symptoms. During the study periods, nochanges were found in body weight (See FIG. 3). TDV decreased in allcases compared to the pre-values, although the decreases were notsignificant statistically (See FIG. 4). Significant fall in mean BP werefound in all cases at the 1 week (p<0.01), 2 week (p<0.05) and 4 week(p<0.01) periods compared to the pre-values, respectively (See FIG. 5).Significant increase in sodium removals were found in the day on lowsodium dialysate in all cases (p<0.001) (See FIG. 6). Serum sodiumlevels were decreased significantly at the i week (p<0.01), 2 week(p<0.05) and 3 week (p<0.05) periods compared to the pre-values,respectively (See FIG. 7). Plasma osmolality were decreased at the 1week and 2 week periods significantly (p<0.05, respectively) (See FIG.8). Significant decrease in ANP levels were found at I week (p<0.5) (SeeFIG. 9), while significant decrease in c-GMP levels were found at the 1week and 2 week periods (p<0.05, respectively) (See FIG. 10). On theother hand, significant increase in PRA was found at 1 week (p<0.05)(See FIG. 11). No statistical changes were found in PAC, NEp and AVPlevels during the study (See FIGS. 12-14).

After starting the study, six of the patients noticed a decrease of drymouth, which felt comfortable. Therefore, they found that water intakewas decreased. Facial and leg edema revealed before the study in allcases were improved or decreased in seven of the patients at the end ofthe study.

Discussion

In order to study the clinical effect of lower sodium concentrationdialysate, 120 mEq/l sodium dialysate was applied to patients instead ofthe standard dialysate (Na:132mEq/1). As a result, no changes were foundin body weight, nor TDV. However, significant fall in BP were found, andsignificant increase in trans-peritoneal sodium removals were achievedafter starting the low sodium dialysate. The changes in ANP and itssecond-messager, c-GMP levels, reflect the intra-atrial pressure andvolume expansion even in patients with end-stage renal failure.Therefore, the decreased levels in ANP and c-GMP found in patients, maysuggest the improvement of intra-vascular volume overload in thesecases, and may explain the fall in BP. The activation in PRA and theincrease in PAC and NEp levels may result from the decrease of vascularvolume and the fall in BP. Most patients noticed that their dry mouthdecreased and they stopped excess water drinking. Supposedly, the fallof plasma osmolality partly produced the decrease of the drynesssensation of the mouth. Nonetheless, this was found even in patients whodid not show the apparent decrease in plasma osmolality. Therefore, itis suggested that the relief of over-loaded sodium could suppress theincrease in plasma osmolality, and excess water drinking.

Thus, low sodium dialysate (120mEq/l) can effectively be used for thecorrection of overhydration, and the control of hypertension.

It should be understood that various changes and modifications to thepresently preferred embodiments described herein will be apparent tothose skilled in the art. Such changes and modifications can be madewithout departing from the spirit and scope of the present invention andwithout diminishing its attendant advantages. It is therefore intendedthat such changes and modifications be covered by the appended claims.

We claim:
 1. A peritoneal dialysis solution For providing a sustainedosmotic gradient comprising:an osmotic agent including at least onepolypeptide; and sodium in a concentration that is less than a sodiumplasma concentration in a renal patient who is to receive the solution.2. The peritoneal dialysis solution of claim 1 wherein the solution hasa total osmolality of 300 to about
 500. 3. The peritoneal dialysissolution of claim 1 wherein the sodium comprises approximately 35 toabout 125 (meq/L).
 4. The peritoneal dialysis solution of claim 1wherein the osmotic agent has an osmolality of not more than 200(mOsm/L) and the solution further comprises:0.0 to about 4.0 (% w/v)dextrose; 0 to about 120 (mEq/L) sodium; 0 to about 100 (mEq/L)chloride; 0 to about 45 (mEq/L) lactate; 0 to about 45 (mEq/L)bicarbonate; 0.0 to about 4.0 (mEq/L) calcium; and 0.0 to about 4.0(mEq/L) magnesium.
 5. A method for providing peritoneal dialysis to apatient comprising the step of administering a solution including sodiumand an osmotic agent including at least one polypeptide to a patient,the sodium level being less than a plasma sodium concentration of thepatient.
 6. The method of claim 5 wherein the patient receives one dwellper day and the solution contains:

    ______________________________________                                        Osmotic agent (mOsm/L)                                                                             1-200                                                    Dextrose (% w/v)    1.0-4.0                                                   Sodium (mEq/L)       35-120                                                   Chloride (mEq/L)     3-82                                                     Combination of lactate and                                                                        35-40                                                     bicarbonate (mEq/L)                                                           Calcium (mEq/L)     2.5-3.5                                                   Magnesium (mEq/L)   0.5-1.5                                                   Total osmolality (mOsm/L)                                                                         300-500                                                   ______________________________________                                    


7. The method of claim 5 wherein the solution contains:

    ______________________________________                                        Osmotic agent (mOsm/L)                                                                             1-200                                                    Dextrose (% w/v)    1.0-4.0                                                   Sodium (mEq/L)      100-125                                                   Chloride (mEq/L)    55-87                                                     Combination of lactate and                                                                        35-40                                                     bicarbonate (mEq/L)                                                           Calcium (mEq/L)     2.5-3.5                                                   Magnesium (mEq/L)   0.5-1.5                                                   Total osmolality (mOsm/L)                                                                         300-500                                                   ______________________________________                                    


8. The method of claim 5 wherein the patient receives one dwell per dayand the solution contains:

    ______________________________________                                        Osmotic agent (mOsm/L)                                                                             1-200                                                    Dextrose (% w/v)    1.0-4.0                                                   Sodium (mEq/L)      35-85                                                     Chloride (mEq/L)     0-100                                                    Combination of lactate and                                                                        30-45                                                     bicarbonate (mEq/L)                                                           Calcium (mEq/L)     0.0-4.0                                                   Magnesium (mEq/L)   0.0-4.0                                                   Total osmolality (mOsm/L)                                                                         300-500                                                   ______________________________________                                    


9. The method of claim 5 wherein the solution contains:

    ______________________________________                                        Osmotic agent (mOsm/L)                                                                             1-200                                                    Dextrose (% w/v)    1.0-4.0                                                   Sodium (mEq/L)       90-130                                                   Chloride (mEq/L)    39-95                                                     Combination of lactate and                                                                        35-45                                                     bicarbonate (mEq/L)                                                           Calcium (mEq/L)     0.0-4.0                                                   Magnesium (mEq/L)   0.0-2.0                                                   Total osmolality (mOsm/L)                                                                         300-500                                                   ______________________________________                                    


10. A method for allowing increased salt intake in a diet of a dialysispatient comprising the step of administering to the dialysis patient aperitoneal dialysis solution comprising an osmotic agent that includesat least one polypeptide and sodium in a concentration that is less thana sodium concentration in the dialysis patient who is to receive thesolution.